140 TRANSACTIONS OF THE ILLINOIS 



ist. In having the mouth formed for sucking, by being prolonged 

 into a slender, horny, jointed tube, which arises far back under the breast, 

 apparently between the front and middle legs. 



2d. In not undergoing a complete transformation, as do the beetles, 

 butterflies, etc.; the larvae and pupae being similar in form to the perfect 

 insect. 



3d. In having but two joints in the tarsi or feet. 



4th. In having the antennae longer than the head, and composed of 

 file-form joints. 



5th. In the fact that the winged individuals always have four wings. 



6th. In the fact that all live upon the juices of plants. 



7th. In their small size, no species of our country exceeding one- 

 fourth of an inch in length of body, while many fall considerably short 

 of one-tenth of an inch. 



The character of the mouth and of the wings, and the fact that they 

 do not undergo a complete transformation, place them in the order 

 HoMOPTERA, which also includes the Seventeen-year Locusts and other 

 Cicadas or Harvest-flies, Tree-hoppers, Leaf-hoppers, etc. 



The Plant and Bark-lice are usually placed by entomologists in one 

 distinct section of this order, these two groups constituting the second 

 section of the order, while all the rest are contained in the first section. 

 These two divisions are distinguished from each other chiefly by the 

 position of the beak or mouth. 



This section has been variously divided and arranged by different 

 authors, according to the characters which they conceived to be of most 

 importance. For present purposes the arrangement indicated in the 

 following brief synoptical table will suffice, although not the latest. 



SEC. II. PLANT AND BARK LICE. 



The beak arising apparently from the breast between the anterior 

 and middle legs ; tarsi, or feet, not more than two-jointed, sometimes 

 with but one joint. 



A. A beak present in both sexes ; wings, when present, four; never changing, in 



the perfect state, into an apparently lifeless scale. {Plant-lice.) 



B. The four wings transparent ; the pupa; active and not scale-like. 



C. Possessing the power of leaping ; the antennii; thread-like, composed of nine or 



ten joints, and tipped at the end with two minute bristles, i Fam. PsYLLlD.i;. 



CC. Not possessing the power of leaping; the antennre usually six or seven-jointed, 



without the two bristles at the tip. 2 Fam. Aphid.i:."' 

 B B. The four wings opaque, farinose; the pupa inactive and scale-like. 3 Fam. 



AlEURODID/K. 



A A. No beak in the perfect male; wings present in the male only, and but two ; 

 female changing in the perfect state into an apparently lifeless scale. {Bark- 

 lice.) 4 Fam. CocciD/E. 



* Note. — I follow Westvvood in the method of writing this name ; perhaps it would be more 

 correct if written AphididcF , but the form I have adopted is that originally given by Leech, adopted by 

 Westwood, Fitch, Packard and others, while Aphididce is the form adopted in Curtis' Farm Insects, and 

 by Harris. 



